<?php
/**
 * CPagination class file.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright 2008-2013 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

/**
 * CPagination represents information relevant to pagination.
 *
 * When data needs to be rendered in multiple pages, we can use CPagination to
 * represent information such as {@link getItemCount total item count},
 * {@link getPageSize page size}, {@link getCurrentPage current page}, etc.
 * These information can be passed to {@link CBasePager pagers} to render
 * pagination buttons or links.
 *
 * Example:
 *
 * Controller action:
 * <pre>
 * function actionIndex(){
 *     $criteria=new CDbCriteria();
 *     $count=Article::model()->count($criteria);
 *     $pages=new CPagination($count);
 *
 *     // results per page
 *     $pages->pageSize=10;
 *     $pages->applyLimit($criteria);
 *     $models=Article::model()->findAll($criteria);
 *
 *     $this->render('index', array(
 *     'models' => $models,
 *          'pages' => $pages
 *     ));
 * }
 * </pre>
 *
 * View:
 * <pre>
 * <?php foreach($models as $model): ?>
 *     // display a model
 * <?php endforeach; ?>
 *
 * // display pagination
 * <?php $this->widget('CLinkPager', array(
 *     'pages' => $pages,
 * )) ?>
 * </pre>
 *
 * @property integer $pageSize Number of items in each page. Defaults to 10.
 * @property integer $itemCount Total number of items. Defaults to 0.
 * @property integer $pageCount Number of pages.
 * @property integer $currentPage The zero-based index of the current page. Defaults to 0.
 * @property integer $offset The offset of the data. This may be used to set the
 * OFFSET value for a SQL statement for fetching the current page of data.
 * @property integer $limit The limit of the data. This may be used to set the
 * LIMIT value for a SQL statement for fetching the current page of data.
 * This returns the same value as {@link pageSize}.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @package system.web
 * @since 1.0
 */
class CPagination extends CComponent
{
    /**
     * The default page size.
     */
    const DEFAULT_PAGE_SIZE = 10;
    /**
     * @var string name of the GET variable storing the current page index. Defaults to 'page'.
     */
    public $pageVar = 'page';
    /**
     * @var string the route (controller ID and action ID) for displaying the paged contents.
     * Defaults to empty string, meaning using the current route.
     */
    public $route = '';
    /**
     * @var array of parameters (name=>value) that should be used instead of GET when generating pagination URLs.
     * Defaults to null, meaning using the currently available GET parameters.
     */
    public $params;
    /**
     * @var boolean whether to ensure {@link currentPage} is returning a valid page number.
     * When this property is true, the value returned by {@link currentPage} will always be between
     * 0 and ({@link pageCount}-1). Because {@link pageCount} relies on the correct value of {@link itemCount},
     * it means you must have knowledge about the total number of data items when you want to access {@link currentPage}.
     * This is fine for SQL-based queries, but may not be feasible for other kinds of queries (e.g. MongoDB).
     * In those cases, you may set this property to be false to skip the validation (you may need to validate yourself then).
     * Defaults to true.
     * @since 1.1.4
     */
    public $validateCurrentPage = true;

    private $_pageSize = self::DEFAULT_PAGE_SIZE;
    private $_itemCount = 0;
    private $_currentPage;

    /**
     * Constructor.
     * @param integer $itemCount total number of items.
     */
    public function __construct($itemCount = 0)
    {
        $this->setItemCount($itemCount);
    }

    /**
     * @return integer number of items in each page. Defaults to 10.
     */
    public function getPageSize()
    {
        return $this->_pageSize;
    }

    /**
     * @param integer $value number of items in each page
     */
    public function setPageSize($value)
    {
        if (($this->_pageSize = $value) <= 0)
            $this->_pageSize = self::DEFAULT_PAGE_SIZE;
    }

    /**
     * @return integer total number of items. Defaults to 0.
     */
    public function getItemCount()
    {
        return $this->_itemCount;
    }

    /**
     * @param integer $value total number of items.
     */
    public function setItemCount($value)
    {
        if (($this->_itemCount = $value) < 0)
            $this->_itemCount = 0;
    }

    /**
     * @return integer number of pages
     */
    public function getPageCount()
    {
        return (int)(($this->_itemCount + $this->_pageSize - 1) / $this->_pageSize);
    }

    /**
     * @param boolean $recalculate whether to recalculate the current page based on the page size and item count.
     * @return integer the zero-based index of the current page. Defaults to 0.
     */
    public function getCurrentPage($recalculate = true)
    {
        if ($this->_currentPage === null || $recalculate) {
            if (isset($_GET[$this->pageVar])) {
                $this->_currentPage = (int)$_GET[$this->pageVar] - 1;
                if ($this->validateCurrentPage) {
                    $pageCount = $this->getPageCount();
                    if ($this->_currentPage >= $pageCount)
                        $this->_currentPage = $pageCount - 1;
                }
                if ($this->_currentPage < 0)
                    $this->_currentPage = 0;
            } else
                $this->_currentPage = 0;
        }
        return $this->_currentPage;
    }

    /**
     * @param integer $value the zero-based index of the current page.
     */
    public function setCurrentPage($value)
    {
        $this->_currentPage = $value;
        $_GET[$this->pageVar] = $value + 1;
    }

    /**
     * Creates the URL suitable for pagination.
     * This method is mainly called by pagers when creating URLs used to
     * perform pagination. The default implementation is to call
     * the controller's createUrl method with the page information.
     * You may override this method if your URL scheme is not the same as
     * the one supported by the controller's createUrl method.
     * @param CController $controller the controller that will create the actual URL
     * @param integer $page the page that the URL should point to. This is a zero-based index.
     * @return string the created URL
     */
    public function createPageUrl($controller, $page)
    {
        $params = $this->params === null ? $_GET : $this->params;
        if ($page > 0) // page 0 is the default
            $params[$this->pageVar] = $page + 1;
        else
            unset($params[$this->pageVar]);
        return $controller->createUrl($this->route, $params);
    }

    /**
     * Applies LIMIT and OFFSET to the specified query criteria.
     * @param CDbCriteria $criteria the query criteria that should be applied with the limit
     */
    public function applyLimit($criteria)
    {
        $criteria->limit = $this->getLimit();
        $criteria->offset = $this->getOffset();
    }

    /**
     * @return integer the offset of the data. This may be used to set the
     * OFFSET value for a SQL statement for fetching the current page of data.
     * @since 1.1.0
     */
    public function getOffset()
    {
        return $this->getCurrentPage() * $this->getPageSize();
    }

    /**
     * @return integer the limit of the data. This may be used to set the
     * LIMIT value for a SQL statement for fetching the current page of data.
     * This returns the same value as {@link pageSize}.
     * @since 1.1.0
     */
    public function getLimit()
    {
        return $this->getPageSize();
    }
}